Market research firm NPD has announced that the iPhone 3G was the leading handset purchased by adult consumers in the U.S. during the third quarter of 2008. The move strips the top dog title away from the previously top-ranked Motorola RAZR and puts an end to the RAZR's three-year run atop the market according to AppleInsider.

So that makes the list:

iPhone 3G

Motorola RAZR

Research in Motion Blackberry Curve

LG's Rumor

LG enV2

"The displacement of the RAZR by the iPhone 3G represents a watershed shift in handset design from fashion to fashionable functionality," said Ross Rubin, director of industry analysis for NPD. "Four of the five best-selling handsets in the third quarter were optimized for messaging and other advanced Internet features."

The news comes just weeks after Apple announced that Apple outsold Research In Motion (RIM) in revenue (not units) last quarter after just 15 months in the market. Apple is now the world’s third largest mobile phone supplier, again in revenue, not units. The breakdown is:

Nokia $12.7 billion

Samsung $5.9 billion

Apple $4.3 billion

Sony Ericsson $4.2 billion

LG $3.4 billion

Motorola $3.2 billion

RIM $2.1 billion

Update: TechCrunch is reporting that the iPhone is twice as reliable as the BlackBerry after one year of ownership, according to a new study by SquareTrade. SquareTrade looked at the failure rates of 15,000 phones covered under its plans and stated that the malfunction rate for iPhones after one year is 5.6 percent, compared to 11.2 percent for the BlackBerry and 16.2 percent for the Treo. The full report is available at the SquareTrade site.